You did challenge me some. But what does that say about the mindset of educated theologians who probably know more about religion and scripture than you do? And I'll leave it at that.
It says that theology is subject to the same ivory tower pressures all other disciplines are; which lead to highly educated specialists to be ignorant, naive and oversimplifying about other disciplines; or ideologically driven in their crossovers.
I am very used to that in my own field: people who are experts (or at least, highly educated) on my field or close fields, who are nonetheless quite ignorant, naive or oversimplifying about other disciplines; or ideologically driven on what they take from them. So I'm never especially surprized that someone truly knows a lot about X and still knows little about Y and even "knows" false things about Z. Theologians are no better than other people on this. I don't know if they're "worse", and maybe they are, but obviously they at least will have different blind spots than other disciplines do. (A huge one is the reliance on written accounts as accurate historical narrative: that's how they keep people, including most otherwise consistently skeptical Atheists, believing in the historical existence of Jesus). But all disciplines in their modern forms are insular. The "Renaissance Man" is dead.
Sea elephants routinely rape as their means of having sex. They quite often kill small juveniles by trampling over them. They also kill female juveniles upon raping them, although this is more accidental than intentional (after all, they're seeking to reproduce, not to kill). If "we" had evolved from sea elephants, you would probably be saying rape is moral and death from rape is moral, and looking for evolutionarily friendly mechanisms why these "objectively" moral mores were the ones we evolved into.
Mantises and many spiders, while they engage in consensual sex, kill their partner upon completion of the coitus.
Several species of fish, famously clownfish, have a transexual life cycle.
On other species of fish, the male attaches to the female permanently and slowly becomes an appendage of hers, progressively losing all his autonomos organs except his sperm production.
The cuckoo relies on other species to provide for their young.
The female bedbug doesn't have a vagina or equivalent, so the male has to actively stab her belly to create a hole to fuck her. (And you thought circumcision was bad).
A majority of fish and reptiles entirely abandon their young upon laying their eggs. The egg is vulnerable to predation. The newborn too, and they also have to learn everything by themselves from scratch.
Social insects show very interesting sexual mores: male bees die upon reproducing, and upon colony succession, workers have all the remaining princesses killed in their own cells; female termites become literal egg factories once they get pregnant; the silent majorities of workers and soldiers will give their whole lives to work without sex.
And of course, though we are not alone in this, most species don't have sex for fun.
So... if you look for the sources of sexuality related morality in evolution, first you have to show that the customs of genus Homo indeed are more moral than those of other genera. The concealment of female fertility, by the way, is exceptional in the whole sphere of living beings (I don't dare say unique, but I personally know of no other species where it happens) to begin with.